bgp 6-3 cont. again...

when i was in marine boot camp our senior drill instructor, when pissed off at our collective dumbassness, would yell at us to get outside in the pit so he could pt the hell out of us...  once assembled there he'd announce:

mountain climbers, again... begin...

again, begin... always again, begin... as if it never ended...

the links from the isp to the individual routers are not known by each router individually... let's fix that...

router bgp 200
netw 192.168.1.0 mask 255.255.255.252
netw 192.168.1.4 mask 255.255.255.252

now the isp will be able to ping the internal links without the ping contortion through it's loopback...

isp#sh ip bgp
BGP table version is 5, local router ID is 192.168.100.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,
              x best-external, a additional-path, c RIB-compressed,
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *   172.16.0.0       192.168.1.6              0             0 64512 i
 *>                   192.168.1.2              0             0 64512 i
 *>  192.168.1.0/30   0.0.0.0                  0         32768 i
 *>  192.168.1.4/30   0.0.0.0                  0         32768 i
 *>  192.168.100.0    0.0.0.0                  0         32768 i

sj2#sh ip route bgp                  

Gateway of last resort is not set

      192.168.1.0/24 is variably subnetted, 3 subnets, 2 masks
B        192.168.1.4/30 [20/0] via 192.168.1.1, 00:05:34
B     192.168.100.0/24 [20/0] via 192.168.1.1, 01:46:33

sj1#sh ip route bgp

Gateway of last resort is not set

      192.168.1.0/24 is variably subnetted, 3 subnets, 2 masks
B        192.168.1.0/30 [20/0] via 192.168.1.5, 00:06:38
B     192.168.100.0/24 [20/0] via 192.168.1.5, 01:47:06

foreach address {
192.168.100.1
192.168.1.5
192.168.1.6
172.16.64.1
172.16.1.1
172.16.1.2
192.168.1.1
192.168.1.2
172.16.32.1
} { ping $address}

Sending 5, 100-byte ICMP Echos to 192.168.100.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/1 ms
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.1.5, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 8/8/8 ms
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.1.6, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 4/4/4 ms
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.16.64.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 4/5/8 ms
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.16.1.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 4/6/8 ms
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.16.1.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/4 ms
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.1.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 8/8/12 ms
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.1.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 4/4/4 ms
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.16.32.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 4/4/4 ms
isp(tcl)#


self help

next hop self tells a router to change the NEXT_HOP attribute of routes received from an external peer to it's own address. This function is used when the igp has no knowledge of the external next hop address

ok...

sj2#sh ip bgp
BGP table version is 13, local router ID is 172.16.32.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,
              x best-external, a additional-path, c RIB-compressed,
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *>  172.16.0.0       0.0.0.0                  0         32768 i
 * i                  172.16.64.1              0    100      0 i
 r i 192.168.1.0/30   192.168.1.5              0    100      0 200 i
 r>                   192.168.1.1              0             0 200 i
 * i 192.168.1.4/30   192.168.1.5              0    100      0 200 i
 *>                   192.168.1.1              0             0 200 i
 * i 192.168.100.0    192.168.1.5              0    100      0 200 i
 *>                   192.168.1.1              0             0 200 i


we want the gateway to the above networks to be the other router in the igp, not the external AS... the semantics are confusing... so what's this self shit?

this on
http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a00800c95bb.shtml#bgpnexthop


The next-hop-self command allows you to force BGP to use a specific IP address as the next hop.


Updates meant for the specified system or peer group are forced to advertise this router as the next hop.

next-hop-self means that this router is the next hop to get to the identified neighbor, as below...

sj1

router bgp 64512
neighbor 172.16.32.1 next-hop-self

i am the next hop to get to the identified neighbor

sj2

router bgp 64512
neighbor 172.16.64.1 next-hop-self

reset softly...

i am not altogether thrilled with this output...

i have a long way to go here... and the semantics of this last excursion have set me back...

one of the themes of this lab is that the link from sj2 to isp is expensive and that the link from sj1 should be preferred as a result... set a route map to prefer the link to sj1

route-map preferred_link permit
set local-pref 150
exit
router bgp 64512
neigh 192.168.1.5 route-map preferred_link in

sj2

route-map not_preferred permit
set local-pref 125
exit
router bgp 64512
neigh 192.168.1.1 route-map not_preferred in

reset, of course...